fix(stats): project trusted mileage source endpoint from metadata

.superpowers/sdd/task-3-report.md

@@ -48,3 +48,21 @@ Both passed.
 ## Commit
 
 `aa12317b5` - `feat(stats): project elected mileage source`
+
+## Fix (reviewer findings)
+
+Applied the reviewer correction for the trusted source endpoint contract:
+
+- In `go/vehicle-gateway/internal/stats/source_mileage.go`, `projectDailyMileageSQL` now writes `trusted_source_endpoint` from `vehicle_data_source.latest_source_endpoint` via `COALESCE(NULLIF(ds.latest_source_endpoint, ''), s.source_endpoint)` so latest connection metadata is authoritative with a simple fallback.
+- Replaced hardcoded quality predicate with the existing constant using `s.quality_status = '` + QualityOK + `'` in `projectDailyMileageSQL`.
+- Updated `go/vehicle-gateway/internal/stats/source_mileage_test.go` to assert both the endpoint expression and constant-based quality predicate.
+
+Validation commands:
+
+```bash
+cd go/vehicle-gateway && go test ./internal/stats -run TestProjectDailyMileageSelectsCandidateAndMarksSource -count=1
+# PASS: lingniu-vehicle-ingest/go/vehicle-gateway/internal/stats
+
+cd go/vehicle-gateway && go test ./internal/stats -count=1
+# PASS: lingniu-vehicle-ingest/go/vehicle-gateway/internal/stats
+```

go/vehicle-gateway/internal/stats/source_mileage.go

@@ -192,7 +192,7 @@ SELECT
   s.latest_total_mileage_km,
   s.source_key,
   s.phone,
-  s.source_endpoint,
+  COALESCE(NULLIF(ds.latest_source_endpoint, ''), s.source_endpoint),
   s.sample_count
 FROM vehicle_daily_mileage_source s
 LEFT JOIN vehicle_data_source ds
@@ -200,7 +200,7 @@ LEFT JOIN vehicle_data_source ds
 WHERE s.vin = ?
   AND s.stat_date = ?
   AND s.protocol = ?
-  AND s.quality_status = 'OK'
+  AND s.quality_status = '` + QualityOK + `'
   AND s.daily_mileage_km BETWEEN 0 AND ?
   AND COALESCE(ds.enabled, 1) = 1
 ORDER BY COALESCE(ds.trust_priority, 100),

go/vehicle-gateway/internal/stats/source_mileage_test.go

@@ -102,8 +102,9 @@ func TestProjectDailyMileageSelectsCandidateAndMarksSource(t *testing.T) {
 		"FROM vehicle_daily_mileage_source s",
 		"LEFT JOIN vehicle_data_source ds",
 		"ORDER BY COALESCE(ds.trust_priority, 100)",
-		"s.quality_status = 'OK'",
+		"s.quality_status = '" + QualityOK + "'",
 		"s.daily_mileage_km BETWEEN 0 AND",
+		"COALESCE(NULLIF(ds.latest_source_endpoint, ''), s.source_endpoint)",
 	} {
 		if !strings.Contains(projectFinal, want) {
 			t.Fatalf("project query missing %q: %s", want, projectFinal)